There are a couple of possibilities.
Streetlife.com seems to cover most places and could possibly distribute the sort of info that you have in mind. They literally live up to the name and cover very small, as well as larger, events.
The other possibility is to use your local Community Voluntary Services group. (If you don’t belong you ought to!) Cost is low and they have access to all kinds of help and services. You can probably get a free site from them that you can develop yourself or, as is our case locally, they email out details of events each week to member groups completely free of charge. I can only speak for ours, but there is a mass of help and advice available, including where to obtain grants, and basic ways of running a group – and keeping within the law. I think we get charged around £ 25 – 40 a year as a voluntary group